In a double-whammy sort of blow to Lakshmi Mittal,value of three houses owned by his family on UKs costliest street has nearly halved in about six months,while the NRI steel tycoons stock market net worth has plunged to about one-third in the same period.

The citys Kensington Palace Gardens,where Mittal family has purchased three houses,was named as the costliest in a ranking of Britains 20 highest-value streets released by property website Zoopla in July last year. The ranking had put the average price of a house on the street at that time at 41.4 million pounds,which has now plunged to 23.5 million pounds,although Kensington Palace Gardens is still the costliest street in Britain,as per the latest data available with Zoopla. On this private avenue,lined with trees and dotted with foreign embassies,Mittal purchased a 70-million-pound house for his daughter Vanisha in June last year.

This purchase came close after a world record 117 million pound mansion bought for his son Aditya,while about four years ago,Mittal had purchased his first house on the Billionaires Row for about 57 million pounds.

At the time of the purchase of the familys last on the street,the combined value of the three properties owned by Mittal family on this street is said to be valued at about 440 million pounds  nearly 200 million pounds more than the amount paid for these properties over a period of four years. While the exact values of these houses are not known,the average price of a residential property in this area has nearly halved in the past six months,as per Zoopla data.

Taking the decline in average price of Kensington Palace Gardens houses into account,the three houses owned by the Mittal value would be worth about 200 million dollars,an amount almost equivalent to the purchase prices.

The fall in average home prices at Mittal street coincides with a sharp plunge in the stock market valuation of the worlds largest steel maker ArcelorMittal,majority owned by the Mittal family.

The Central London street,also known as Billionaires Row,was once home to late Princess Diana,while its current residents include a number of high-flying celebrities. Zoopla had said in a report compiled last month that British homes were estimated to have lost over half a trillion pounds of their values in 2008.